Remainder when (x−1)n is divided by x is (−1)n ∴(17)200=(18−1)200 ∴ Remainder =(−1)200=1 Alternate Method: an−bn is completely divisible by a + b. If n is an even number in the case of 17200÷18 17200−1200 is completely divisible by 17+1=18 Here, 1 is remainder. Or in other words if an is divided by a+1 and n is even number then it always left 1 as remainder.